2023 day 15

2023/15/Main1.hs

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+import           Data.Bits ((.&.))
+import           Data.Char (ord)
+import           Data.List (foldl')
+import           Data.List.Split (splitOn)
+
+getHash :: String -> Int
+getHash = foldl' (\acc x -> (acc + ord x) * 17 .&. 255) 0
+
+main :: IO ()
+main = print . sum . map getHash . splitOn "," . concat . lines
+  =<< readFile "data.txt"

2023/15/Main2.hs

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+import           Data.Bits ((.&.))
+import           Data.Char (ord)
+import           Data.List (deleteBy, findIndex, foldl')
+import           Data.List.Split (splitOn)
+import qualified Data.Vector as V
+import qualified Data.Vector.Mutable as MV
+import           Data.Vector (Vector, MVector)
+
+type Command = (String, Maybe Int)
+
+getHash :: String -> Int
+getHash = foldl' (\acc x -> (acc + ord x) * 17 .&. 255) 0
+
+parseCommand :: String -> Command
+parseCommand s
+  | last s == '-' = (init s, Nothing)
+  | otherwise = (a, Just . read $ b)
+  where
+    (a:b:_) = splitOn "=" s
+
+sumFocusPower :: Vector (Vector (String, Int)) -> Int
+sumFocusPower = timesIndexAndSum . V.map (timesIndexAndSum . V.map snd)
+  where
+    timesIndexAndSum = V.foldl' (+) 0 . V.imap ((*) . succ)
+
+performCommand
+  :: MVector MV.RealWorld (Vector (String, Int)) -> Command -> IO ()
+performCommand boxes (label, mFoc) = maybe performDash performEquals mFoc
+  where
+    boxN = getHash label
+
+    readBox = MV.read boxes boxN
+
+    writeBox = MV.write boxes boxN
+
+    findPred = (== label) . fst
+
+    performDash = writeBox . V.filter (not . findPred) =<< readBox
+
+    performEquals foc = do
+      box <- readBox
+      let newLens = (label, foc)
+          addNewLens = V.snoc box newLens
+          swapLens i = V.modify (\v -> MV.write v i newLens) box
+      writeBox . maybe addNewLens swapLens . V.findIndex findPred $ box
+
+main :: IO ()
+main = do
+  commandStrs <- splitOn "," . concat . lines <$> readFile "data.txt"
+  boxes <- MV.replicate 256 V.empty
+  mapM_ (performCommand boxes . parseCommand) commandStrs
+  print . sumFocusPower =<< V.unsafeFreeze boxes